High voltage processing of cathode ray tubes

ABSTRACT

A cathode ray tube processing conveyor, comprising means for energizing the cathodes and applying a high voltage to the high voltage accelerating electrodes of the tubes, is provided with two rows of magnetic field coils of alternating polarities mounted on opposite sides of the conveyor and adjacent to the path of the tubes therealong, for deflecting the beams and thereby preventing damage to the screen during the application of the high voltage.

United States Patent Gronka [54] HIGH VOLTAGE PROCESSING OF CATHODE RAY TUBES [72] Inventor: Edward Anthony Gronka, West Nanticoke, Pa.

[73] Assignee: RCA Corporation [22] Filed: Dec. 28, 1970 [21] Appl. No.: 101,794

[52] U.S. Cl. ..316/26, 29/2511, 316/1 [51] Int. Cl ..H0lj 9/00 [58] Field of Search ..29/25.1, 25.11; 316/1, 22,

[56] References Cited UNITED STATES PATENTS 3,067,349 12/1962 Kasperowiczetal...;.29/25.ll

[151 3,698,786 [451 Oct. 17,1972

Mengel ..316/1 Primary Examiner-John F L Campbell Assistant ExaminerRichard Bernard Lazarus Attorney-Glenn H. Bruestle [5 7] ABSTRACT A cathode ray tube processing conveyor, comprising means for energizing the cathodes and applying a high voltage to the high voltage accelerating electrodes of the tubes, is provided with two 'rows of magnetic field coils of alternating polarities mounted on opposite sides of the conveyor and adjacent to the path of the tubes therealong, for deflecting the beams and thereby preventing damage to the' screen during the application of the high voltage."

6 Claims, 6 Drawing Figures Angelucci et al ..316/1- PATENTED I972 3.698.786

sum 1 or 3 I N VEN TOR.

' Edward A. Gronka AGENT PATENTEDHBI 11 m2 3 698 7:86

SHEET 3 BF 3 90 62 62 i i 46 52 88'?" n i 34 l I INVENTOR. g Edward AGronka AGENT men VOLTAGE PROCESSING OF CATHODE RAY TUBES BACKGROUND OF THE INVENTION Thepresent invention relates to improvements in methods of high voltage processing of cathode ray tubes in general, and particularly those cathode ray tubes having electron guns, e.g., Einzel type guns, in which the accelerating electrode next to the low-voltage screen grid is normally operated at the ultor, or highest, voltage applied to the tube.

In the manufacture of cathode ray tubes, it is custotrodes (which are normally connected together) are" connected to a high voltage source in excess of 50 KV (for a tube having a normal ultor operating voltageof 25 KV) for about 2 minutes, to burnoff loose particles which may extend between electrodes in the tube. In the hot-shot process, the cathodes are activated by heating them to an abnormally high temperature, e.g-., by applying 14 volts to cathode heaters-which are normally operated at 8 volts, for about 2 minutes, with all of the other gun electrodes and the internal conductive coatings floating. In the aging process, voltages areapplied to all of the electrodes, except the high voltage electrodes and internal'conductive coatings, for about 60 minutes, as follows: a normal voltage of about 8 volts is applied to the cathode heaters, a low positive voltage of to volts is applied to the control grids- (Gl), a positive voltage of several hundred volts (e.g.,

+300 volts) is applied to the screen grids (G2), with the other electrodes floating. In each of these processes, no high voltage (velocity) electrons reach the phosphor screen and hence, there is no problem of the screen being damaged by electron bombardment.

Proposals have been made that the normal processing of cathode ray tubes be modified, to improve the high voltage stabilization of completed tubes, to produce a high voltage (velocity) electron beam in the gun region during at least a portion of one of the spot-knock, hot-shot and aging processes. This involves modifying the spot-knock process by applying the high voltage while heating the cathodes, or modifying either the hot-shot or aging processes by applying a high voltage to the high voltage accelerating electrodes during the conventional steps. The high velocity beam must be either cut off (interrupted) or continuously deflected before reaching the screen to prevent burn damage to the screen. The beam can be cut off in the so-called bipotential electron gun, having a G3 focus electrode located next to the G2 screen grid and normally operated at a few thousand volts (e.g., 4,000 volts) and a G4 focus electrode operated at the ultor voltage (e.g., KV), by applying a negative voltage (e.g., 200 volts) with respect to the cathode, to the G3 focus electrode However, in an Einzel (unipotential) gun, for ex-- ample, having G3 and G5 focus electrodes operated at the ultor voltage and an intermediate G4 focus elec- 2 trode operated at a low voltage(n ear cathode potential) the beam cannot be cut off by applyinga negative .voltage to the low-voltage focus G4 electrode. Of

course, the beamcould be deflected continuously during this processing step, by installing a deflection yoke on each tube and feeding deflection voltages to the yokes, to prevent screen bum. However, this would require provision and mounting of a. large number of deflection yokes, e.g., 400 or more per processing conveyor, and additional connections and bus bars on the conveyor, as wellas. deflection voltage supplies toenergize the yokesv SUMMARY OF THE INVENTION Cathode ray tubes are processed, after being-assembled and sealed off, I and while they are transported along a given path, by energizing the cathodes to form electron beams, applying a high voltage to the high voltage accelerating electrodes of the tubes, and

establishing a series of different substantially contiguous magnetic fields at predetermined locations along'the path, vfor deflecting the beams and preventing .damage to the tube screen during application of the high voltage.

Preferably, the magnetic fields are established by two rows of magnetic field coils of alternating polarity mounted on oppositegsides of the tube path and adjacent to the tubes, with the coils on one side staggered with respect to the coils on the other side.

BRIEF DESCRIPTION OF TI-IEDRAWING FIG. 1 is a partial side view, partly in section on'line 1-1 of FIG. 2',-of a cathode ray tube conveyor, including one tube carrier thereof,in which the present invention is incorporated.

FIG. 2 is a partial side view taken at right angles to FIG. l,partly in section on line 2- -2thereof.

FIG. 3 is an enlarged plan view of a portion of the conveyor of FIGS. 1 and 2, partly in section on line 3- 3ofFlG,2. e H

FIG. 4 is a section view taken on line 4-4-of FIG. 1.

FIG. 5 is a circuit showing the method of energizing the magnetic field coils in FIGS. 1, 2 and 4.

FIG. 6 isan enlarged-side view partly in section of an Einzel lens type electron gun.

DETAILED DESCRIPTION THE PREFERRED EMBODIMENT FIG. 1 shows part of a conveyor which may be used to process a series of cathode ray tubes in accordance with the present invention. The conveyor includes a plurality of two-wheel trolleys 10, each of whichis supported by a pair of wheels 12 from the lower flange 14 of an I-beam 16 forming a track for the trolleys 10. The

' trolleys are connected .together at uniformly spaced positions by a flexible connecting chain 18, as shown in FIG. 1. FIG. 1 shows a portion of the conveyor system comprising a single carrier 20 for supporting a cathode ray tube 22 (shown in phantom). The single carrier 20 comprises a pendant 24 pivotally hung at 26 from a trolley 10. A suspension insulator 28 is pivotally hung at 30 from the lower end of pendant 24 and a tube-carrying yoke 21 is pivotally hung at 32 from the lower portion of insulator 28. Insulator 28 includes a large 3 disk 34, e.g., of porcelain, interposed between the pendant24 and the yoke 21. Yoke 21 consists of a pair of arms 36 and 37of metal tubing forming a general C shape, as shown in FIG. 1. The ends of arms 36 and 37 are bent to extend toward each other andboth terminate in arcuate lateral sections 38 and 40 adapted to receiveand support the funnel portion 23 of tube 22, with the neck42 down, by gravity. The trolleys l and carriers 20 are moved along the track 16 by power means such as an electrical motor (not shown) connected to the chain 18. a

Means are provided for spot-knock, hot-shot and aging operations on the tubes 22 during the transporta tion thereof from a loading station to another station at which the processed tubes are tested-This requires the application'of voltages of different amounts ranging up 22, an insulating terminal block 44 is fixed to each side of the pendant 24. Fixed to the terminal blocks 44are contact members 46, 48, 50, S2, 54 and 56, as shown in FlGS. 1 to 3. Each contact member includes a mounting plate 58, a rod 59, a coil spring 60 and a spherical contact 62. Along certain portions of the track 16, brass angle busbars are mounted parallel to the track and in the path of one of the contacts 62. As shown in FIG. 2, each contact 62 of contact members 46 through 56 each respectively contacts a different bus bar numbered 64, 66, 68, 70, 72 and 74, respectively. As shown in FIG. 3, the contacts 46 through 56 extend rearwardly'of the direction of motion of the carriers and at an angle to the respective bus bar. Each contact member is individually connected by a wire 80 (FIG. I) to a different terminal (not shown) in a 'socket82 on tube 22. Wires 80 are formed into a cable 84 extending between the pendant 24 and the socket 82. Cable 84 is suspended at one end from an adjacent trolley by a 1 to 60,000 volts. To supply these voltages to the tubes hook 85 and at the other end by an insulator 86'attached to the yoke section 38. A'high voltage contact through the bus bar 90, contact member 88, metal yoke 21, metal support 40, and a flexible lead 91 .whichis connected to the ultor terminal 92 in the funnel 23 of the tube. The inner end of terminal 92 is connected (not shown) to the internal conducting coating 93 which extends from the screen of the tube across the funnel 23 and partly into the neck 42 where it is connected by a metal bulb spacer 94 to the final electrode (e.g., the G5 electrode in an Einzel gun) of the electron gun 95 (see H0. 6). The leads for all of the other electrodes of the electron gun 95 (except the G3 electrode in an Einzel gun) are brought out through the tube stem to a tube base 96, for connection to a socket (82).

The cathode ray tubes may be processed, as they move successively along the conveyor, substantially in the manner described in the Nash US. Pat. No. 2,917,357 referred to above, that is, by successively subjecting each tube to spot-knock, hot-shot and aging operations, with the following modifications. During one of these operations, a high voltage is applied to a high voltage accelerating electrode in the gun while the cathode is energized to produce an electron beam and a series of variable magnetic fieldsv are established along the path of the tube along the conveyor, to substantially continuously deflect the electron beam and thereby prevent burning of the screen. The high voltage isapplied as described above. The'cathode K is-heated by a conventional heater (not shown) energized by two of the bus bars 64-74, contact members 46-56, and

wires 80.

The series of variable magnetic fields are established at predetermined locations along the conveyor by at least one row of magnetic field coils 100 extending along the conveyor and adjacent to the .path of the tube necks 42. The coils 100 are constructed and arranged along the conveyor so as to produce a composite, substantially continuous, nonQimiform magnetic field therealong, so that the beam of each tube passing along the conveyor is. substantially continuously deflected. Preferably, a row of coils of alternating polarity (FIG. 5) is mounted on each side of the tube path, with the longitudinal axis of each coil perpendicular to the path of the tubes, and with the coils on one side staggered relative to the coils on the other side, as shown in FIGS. 2 and 4. .For example, each coil 100may be made of 1,000 turns of 16 gauge copper wire wound on a 1 inch O.D. core of plastic tubing to form a coil having a diameter of 6 inches and an axial length of 1 inch, with the turns held in place by several ties of nylon lacing cord, or by adhesive tape. Each row of coils 100 may be mounted on the bottom wall 102 of an insulating guard 104, that is usually provided around thetube' strip 1120f plastic may be provided at the upper edge of each plate 108. The coils 100 maybe arranged in groups 101 of four each, with the coils in each group substantially contiguous and the groups spaced apart a short distance. Each group 101 of four coils 100 may be connected, as shown in FIG. 5, to a (SO-cycle, AC source 114' with the voltage adjusted to produce about 6 amperes in each coil. I

FIG. 6 shows the electrode arrangement in'an Einzel gun 95, with which the present invention is particularly useful. The gun comprises a thermionic cathode K, heated by a heater therein (not shown),.a current control grid G1, a screen grid G2, three focusing and accelerating electrodes G3, G4 and G5, with the G3. and G5 electrodes connected together, and thebulb spacer 94 connectedto the wall coating 93. For example, the

gun 95 may be processed under the following conditions:

The negative voltage (-200 volts) applied to the G4 electrode is optional, and is supplied to the conveyor so that either or both Einzel and bi-potential gun tubes can be simultaneously processed on the same conveyor with no changes in the electrical connections to the tubes. The intermediate-voltage G3 focus electrode of a bi-potential gun is connected to the same base terminal as the low-voltage G4 focus electrode of an Einzel gun. Thus, the 200 volts fed to this common terminal will cut off the beam in a bi-potential gun, making it possible, if desired, to interrupt the current supply to the magnetic field coils 100 during the passage of a group of tubes having bi-potential guns only. The series of electrodes K through G5 in FIG. 6 may be associated with a convergence cage 116 common to two other similar series of electrodes to form a conventional three-beam electron gun for a color picture tube of the shadow mask type, for example, in which case the three G5 electrodes are attached to the convergence cage 116.

The use of a series of coils 100 located along the tube processing conveyor, instead of a deflection yoke on each tube, has the following advantages:

1. Only a small number of coils 100 are required for a given conveyor as compared to the number of tubes on the conveyor at a given time; i

2. The necessity for providing means for mounting a yoke on each tube and the time involved in mounting and removing each yoke are eliminated.

3. Each coil 100 may be a simple annular winding, as

compared to the usual complex tube yoke;

. The coils 100 can be energized by a simple voltage source, such as a 60-cycle AC source, with no movable connections such as would be required for energizing individual yokes on the tubes traveling along the conveyor.

While an AC source is preferred for energizing the coils 100, a DC source can be used, providing the coils 100 are arranged so that each tube sees a varying magnetic field as it travels along the conveyor.

I claim:

1. In a method of high-voltage processing of a cathode-ray tube comprising an electron beam source and an electrode for accelerating an electron beam from said source to a luminescent screen, wherein said tube is transported along a given path, said electron beam source is energized, and ahigh voltage with respect to said source is applied to said electrode to give rise to an electron beam during said transport; the improvement comprising the additional step of establishing a series of different substantially-contiguous magnetic fields at predetermined locations along said path forming a composite substantially-continuous non-uniform magnetic field along said path, whereby said tube, in its travel along said path, is subjected to said non-uniform field for substantially continuously deflecting said electron beam to prevent damage to said screen during the application of'said high voltage.

2. The method of claim 1,- wherein said magnetic fields are established by at least one row of magnetic field coils of varying polarity when excited, mounted along said path and adjacent to said tube.

3. The method of claim 1, wherein said magnetic fields are established by two rows of magnetic field coils of alternating polarities when excited, mounted on opposite sides of said path and adjacent to said tube.

4. The method of claim 3, wherein the coils on one side are staggered along said path with respect to the opposite coils.

The method of claim 1, wherein said tube includes a cathode, a control grid and a screen grid, which constitute said beam source, and said accelerating electrode is located next to said screen grid;'and said cathode and control grid are grounded and said screen grid is maintained at ground :50 volts DC during the application of said high voltage to said accelerating electrode.

6. The method of claim 5, wherein said tube further includes a second accelerating electrode spaced along the beam path from said first-named accelerator electrode and connected thereto, and a further electrode interposed between said accelerating electrodes, and wherein a low voltage is applied to said further electrode during the application of said high voltage.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent 3.698. 786 Dated October 17. 1972 Inventofls) Edward Anthonv Gronka It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

IN THE SPECIFICATION:

Column 1, line 18; "2,917,367" should be --2,917,357-,

Column 4, line 18; "90" should be -100---.

Signed and sealed this 27th day of March 1973 (SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents USCOMM-DC 603764 69 330 U,Sv GOVERNMENY PRINTING OFFICE I959 O366-33 

1. In a method of high-voltage processing of a cathode-ray tube comprising an electron beam source and an electrode for accelerating an electron beam from said source to a luminescent screen, wherein said tube is transported along a given path, said electron beam source is energized, and a high voltage with respect to said source is applied to said electrode to give rise to an electron beam during said transport; the improvement comprising the additional step of establishing a series of different substantially-contiguous magnetic fields at predetermined locations along said path forming a composite substantially-continuous non-uniform magnetic field along said path, whereby said tube, in its travel along said path, is subjected to said non-uniform field for substantially continuously deflecting said electron beam to prevent damage to said screen during the application of said high voltage.
 2. The method of claim 1, wherein said magnetic fields are established by at least one row of magnetic field coils of varying polarity when excited, mounted along said path and adjacent to said tube.
 3. The method of claim 1, wherein said magnetic fields are established by two rows of magnetic field coils of alternating polarities when excited, mounted on opposite sides of said path and adjacent to said tube.
 4. The method of claim 3, wherein the coils on one side are staggered along said path with respect to the opposite coils.
 5. The method of claim 1, wherein said tube includes a cathode, a control grid and a screen grid, which constitute said beam source, and said accelerating electrode is located next to said screen grid; and said cathode and control grid are grounded and said screen grid is maintained at ground + or - 50 volts DC during the application of said high voltage to said accelerating electrode.
 6. The method of claim 5, wherein said tube further includes a second accelerating electrode spaced along the beam path from said first-named accelerator electrode and connected thereto, and a further electrode interposed between said accelerating electrodes, and wherein a low voltage is applied to said further electrode during the application of said high voltage. 